Using sharpness image with haar function for urban atmospheric visibility measurement

Abstract

Air quality affects human health, traffic safety and human life quality. The status of air quality can be indicated by the urban atmospheric visibility. The atmospheric visibility is traditionally the human-eye observed maximum distance at which outline of the selected target can be recognized. To replace the traditional measurement for the atmospheric visibility, digital image analysis techniques provide good visibility data which is established by the numerical index. These techniques provide good performance which is defined by the correlation between the observed visual range and the obtained index. In this paper, two high pass filters for atmospheric visibility monitoring are reviewed. Since the performance is affected by non-uniform illumination, such as shadow, a scheme which is called the sharpness image with Haar function is also introduced. Synthetic images, real images and actual atmospheric images are used to show the comparison of the performances. According to the results, the introduced method obtains higher relationship with human observed visibility than the other methods. We also show that obtaining the visibility indices with the proposed procedure can increase the similarity when the observed visibilities are the same. Copyright © Taiwan Association for Aerosol Research.